The ability to determine a user's heart rate is valuable for many fitness applications, including meeting heart rate targets, calculating recovery times, calculating calorie expenditure, etc. Portable and/or wearable heart rate monitors enable the everyday tracking of heart rate. However, the energy consumption required for continuous and/or repetitive heart rate measurement is very high. The problem becomes exacerbated when heart rate measurement is performed with mobile (e.g., portable, handheld, wearable, etc. devices), which have a limited power supply.
To address energy consumption issues, some approaches for reducing energy consumption of heart rate monitors include lowering the duty cycle of the pulses associated with LED light sources. The energy consumption remains high because continuous heart rate monitoring is performed. Thus, continuous heart rate monitoring on a mobile device would leave little energy for other uses.